title: Fast retrospectively triggered local pulse-wave velocity measurements in mice with CMR-microscopy using a radial trajectory.
abstract: BACKGROUND
  The aortic pulse-wave velocity (PWV) is an important indicator of cardiovascular risk. In recent studies MRI methods have been developed to measure this parameter noninvasively in mice. Present techniques require additional hardware for cardiac and respiratory gating. In this work a robust self-gated measurement of the local PWV in mice without the need of triggering probes is proposed.
  
  
  METHODS
  The local PWV of 6-months-old wild-type C57BL/6J mice (n=6) was measured in the abdominal aorta with a retrospectively triggered radial Phase Contrast (PC) MR sequence using the flow-area (QA) method. A navigator signal was extracted from the CMR data of highly asymmetric radial projections with short repetition time (TR=3 ms) and post-processed with high-pass and low-pass filters for retrospective cardiac and respiratory gating. The self-gating signal was used for a reconstruction of high-resolution Cine frames of the aortic motion. To assess the local PWV the volume flow Q and the cross-sectional area A of the aorta were determined. The results were compared with the values measured with a triggered Cartesian and an undersampled triggered radial PC-Cine sequence.
  
  
  RESULTS
  In all examined animals a self-gating signal could be extracted and used for retrospective breath-gating and PC-Cine reconstruction. With the non-triggered measurement PWV values of 2.3±0.2 m/s were determined. These values are in agreement with those measured with the triggered Cartesian (2.4±0.2 m/s) and the triggered radial (2.3±0.2 m/s) measurement. Due to the strong robustness of the radial trajectory against undersampling an acceleration of more than two relative to the prospectively triggered Cartesian sampling could be achieved with the retrospective method.
  
  
  CONCLUSIONS
  With the radial flow-encoding sequence the extraction of a self-gating signal is feasible. The retrospective method enables a robust and fast measurement of the local PWV without the need of additional trigger hardware.
authors.forename: Patrick
authors.initials: P
authors.lastname: Winter
authors.forename: Thomas
authors.initials: T
authors.lastname: Kampf
authors.forename: Xavier
authors.initials: X
authors.lastname: Helluy
authors.forename: Fabian T
authors.initials: FT
authors.lastname: Gutjahr
authors.forename: Cord B
authors.initials: CB
authors.lastname: Meyer
authors.forename: Null
authors.initials: N
authors.lastname: Rommel
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Bauer
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jakob
authors.forename: Volker
authors.initials: V
authors.lastname: Herold
mesh_terms: D000465:Algorithms; D000818:Animals; D001012:Aorta, Abdominal / Q000502:physiology*; D003287:Contrast Media; D005240:Feasibility Studies; D006339:Heart Rate; D007090:Image Interpretation, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine; D008810:Mice, Inbred C57BL; D008853:Microscopy; D023421:Models, Animal; D011237:Predictive Value of Tests; D063177:Pulse Wave Analysis / Q000379:methods*; D056152:Respiratory Rate; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D059289:Vascular Stiffness
chemical_list: D003287:Contrast Media